CVS - Computer Eye Strain
Computer eye strain is the #1 eyestrain complaint in the U.S.
CVS (computer vision syndrome), more commonly known as computer eye strain is a combination of vision problems noticed during and after working long hours on the computer. OSHA describes it as a repetitive strain disorder affecting 90% of U.S. workers on computers daily.
Computers are becoming ubiquitous - they are everywhere and in many forms - all requiring close focused vision.
Next: Nutritional support, diet, & lifestyle tips for computer eye fatigue.
We evolved as hunters and gatherers with vision designed for distance. Our eye muscles are most relaxed using our distance vision. Likewise, we were design to move, and an all-day sitting position is unnatural with consequences on eye and general health.
Staring at your computer for long hours without a break strains your eyes and bodies and results in computer eye strain. Studies show that computer users blink less often, which, Japanese researchers indicate, greatly increases one's risk of developing short-term dry eye syndrome.
HEV Blue Light
While patients are more familiar with vision damage from UVA and UVB light, fewer are aware of the damage to the retina from blue light, or HEV light which is emitted by computer screens. UV light does not penetrate the retina. Blue light does, (hence the recommendation, when outdoors, to wear amber colored sunglasses). In the case of students on computers and computer professionals, the HEV light emitted by computers is another serious source of light that can damage the retina and cause macular degeneration.1, 2
Over time, too much computer use has negative effects that add up including development of farsightedness (presbyopia), nearsightedness (myopia), astigmatism, poor eye-coordination, and ability-to-focus disorders. In addition, sitting in the same position for hours causes neck, back and shoulder stiffness and tension headaches, which in turn cause TMJ (temporomandibular joint) pain. And, of course, the threat of direct damage to the retina from HEV blue light.
- Eyestrain and fatigue
- Blurred or fuzzy vision
- Dizziness, upset stomach
- Difficulty focusing on work
- Headaches and migraine headaches
- Dry, red, or irritated eyes
- Increased myopia (nearsightedness)
- Color vision changes
- Slow ability to refocus
- Excessive tiredness
- Neck strain, shoulder, and upper and lower back pain
- Occasional double vision, or eye-coordination problems
We experience computer eye strain because we may be: too close to computer, spending too many hours at the computer, blinking less, have poor posture, have poor lighting, work with excessive glare.
When our eyes get tired two things happen:
Eye movement: the saccade
Our eyes engage in incredibly rapid constant motion - hundreds of thousands of movements daily, jumping around to parts of the scene before us that command our interest. The information taken in through this continual scanning movement, known as saccade, or micro-saccade, is communicated to the brain and we are able to perceive what is before us without looking at every detail. The continual saccade is both involuntary and efficient as the eyes travel from bit of information to bit of information forming an understanding of the whole.
The function of the saccade is to continually refresh the information sent to the brain. Each saccade causes the image you see to shift to a different part of the retina. This in turn causes the image to adapts to a new neuron in your eye and brain, and in turn, to be intrepreted afresh. So these micro-saccades keep everything visible for you.
Blink rate & eye moisture
The tear film and the blinking process also make vision possible.
Tear film is the moisture-laden surface of the eye2, consisting of three layers (mucus layer, aqueous layer & lipid layer). These interrelated layers work together to remove debris from the surface of the eye, and to lubricate and protect the surface of the eye. Blinking, normally about 10-12 times a minute, is a natural function that helps maintain this tear film.
Blinking momentarily disrupts the saccade. However, when we are intensely focused on one subject, whether while focusing on a computer screen or a watching a deer in the distance, then in order to maintain focus, blinking slows to an average of 3-4 times a minute and the information-gathering saccade is not interrupted.
A slower rate of blinking means that the tear film is not distributed across the surface of the eye and we experience irritation and fatigue. The tear film begins to become unstable and thin after only 10 seconds without blinking.
Muscles of the eye
In order to perform close work several sets of muscles in the eye are active.
- Extraocular muscles cause the eyes to converge to a specific location.
- Ciliary muscles flex the fibrous strands known as the zonules of Zinn which in turn fine-tune the shape of the lens through which light passes on its way to the retina.
- Pupillary muscles which control the diameter of the pupil constrict so that light rays hit only the center of the retina
Just as overuse of our shoulder muscles results in shoulder soreness - short term (acute) and long-lasting (chronic) - overuse of our eyes result in eye fatigue which manifests as asthenopia, computer eye strain, light sensitivity, dry eyes, and other conditions.
When you look at your computer screen for a long time the ciliary muscles remain contracted and eventually get tired and lose their ability to remain contracted. As they loosen the pull on the zonules of Zinn decreases and focus becomes blurry, pain sets in and headaches and other symptoms result.
Furthermore if we wear glasses or contacts then our focus is locked into a specific range. Our eye muscles, not needing to shift for clearer focus, lose their muscle tone and flexibility and their ability to focus accurately.
- dry eyes
- heavy computer use is a risk factor for glaucoma
- ocular migraine
- migraine headaches
- sensitivity to glare
- asthenopia (eye fatigue)
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1. The Chesapeake Bay Waterman Study, Transactions of the American Ophthalmological Society. 1989; 87: 802-853
2. Fifteen-year cumulative incidence of age-related macular degeneration: the Beaver Dam Eye Study, R. Klein, et al, Ophthalmology. 2007 Feb;114(2):253-62; this study continued to 2010.